As known, the ash particles produced by a coal-fed combustion process may comprise a percentage of unburnt carbon. A high percentage of unburnt carbon indicates an incomplete combustion. Furthermore, the size of the ash particles provides further information on the combustion process. Thus, knowing the physical-chemical features of the ash particles in the fume flow produced by a combustion process would allow to control the combustion process itself in real time, so as to improve the process efficiency.
Apparatuses for analyzing particulate matter, e.g. ash particles, in the fume flow of a combustion process in real time are known. These apparatuses include projecting a laser light beam through the fume flow, detecting the intensity of the laser light once it has crossed the fume flow, and determining the concentration of particulate matter in the fumes. Unfortunately, these apparatuses do not allow to determine other physical-chemical features, such as the size of the ash particles or the unburnt carbon percentage in the ash particles.